In the art of the sector different filtering devices are known designed to filter fluid substances coming from meat materials injecting machines. The purpose of the said devices is to conveniently filter the said fluid substances which typically consist in brine, with or without other additives, to condition them so that they can be newly recycled to the injecting machine. The materials which are in suspension in the said fluid substances are from several millimeters thick meat pieces up to microscopic particles. Thus the general strategy of such devices consists in first, passing the fluid through one or more coarse filters and second, passing it through one or more fine filters before it is recycled to the injecting machine.
The main problem to overcome stands in the fact that the filters are gradually clogged by the very particles which are filtered from the fluid. Although for coarse filters this problem is overcome on a nonstop basis by a scraping device and/or pressurised water, up to now, no simple and cheap solution has been found applicable to fine filters without stopping the machine is required.
ES-A-8901853, filed on 2 May 1989 by this applicant, discloses a filtering equipment comprising a first rotatory polyhedral-drum-shaped coarse mesh filter arranged under an inlet of fluid coming from an injecting machine, and a second rotatory cylindrical-drum-shaped fine mesh filter arranged partly submerged in a wrapping tank collecting the fluid coming from the first filter. In an area of the bottom of the said wrapping tank there is a mouth for sucking the fluid through the wall of the said fine mesh filtering drum so that the particles in suspension remain retained on the internal face of the said wall. In an external area emerging from the top part of the said fine mesh drum, there is a cleaning device with pressurised water for the said wall, the said device comprising under the internal face of the said top part, a container for collecting the cleaning water together with the dirtiness preventing that it is mixed with the fluid to be recycled flowing to the injecting machine.
This equipment despite its effectiveness was proven in the practice is complex as for the fine mesh filter cleaning, namely because a rotary drum is required, conveniently driven as well as a cleaning device based on the action of a pressurised fluid which has not to be mixed with the fluid to be filtered. In addition, at relatively long regular periods of time, the cleaning provided by the said automatic device must be completed with a thorough hand cleaning or by means of a machine controlled by an operator.
U.S. Pat. No. 4,622,892, granted on 18 Nov. 1986, discloses a machine for injecting meat materials which incorporates a container with a main filter and a recipient with an auxiliary filter, combined with means for shifting the fluid coming from the injecting machine towards the said container of the said auxiliary filter when it is considered that the main filter has to be cleaned, so that it can be withdrawn for cleaning it by hand or by means of a remote machine, while filtering is carried out through the auxiliary filter. When the main filter is newly operating it is proceeded to clean the auxiliary filter and so on. The outlets of both containers are connected to a pump circulating the fluid, means are provided for commuting the said outlets towards the circulation circuit depending on the filter which is being operated. As well the main as the secondary filters are basket-shaped with flat walls, and an external layer of coarse mesh and an internal layer of fine mesh, adapted to the shape of the containers.
This device allows to clean one of the filters while the other is operating without stopping the machine. However, a hand control of the said means is required for shifting the incoming fluid towards one or the other container as well as from the said means for commuting the outputs thereof towards the circulation circuit to be able to observe the state of dirtiness of the filters and, if it is thought fit, withdraw them for cleaning them.